- This week I got issues with Agilent G1312A binary pump. I run analysis in gradient elution mode. And at the begining of gradient (95% H2O + 5% MeOH) I get pressure fluctuation which causes periodic UV base line fluctuation (2nd picture). Then I start runing gradient and MeOH concentration increases that fluctuation dissappears (1st picture). I want to ask maybe someone had same problem and knows which part most likely can cause this behavior?. I repleaced plunger seals on pump head B and I replaced PTFE frit. Thank you for any tips and suggestions!